1. Field of the Invention
This invention relates to an offset type tractor, with a structural unit, comprising an engine and a transmission casing which is equipped with rear drive wheels and which casing is directly connected to the rear of the engine, said unit being offset to one lateral side of longitudinal center line of the tractor.
2. Description of the Prior Art
A tractor with an engine and a transmission casing serially connected directly to each other is known for making the entire tractor light in weight, in comparison with the tractor in which a longitudinal main frame of substantial length is provided so that the engine and the transmission casing are each mounted thereon and operatively connected with each other. By dispensing with said main frame due to the direct connection of the engine and the transmission casing there is a large reduction in weight. In such tractor serially connected engine and transmission casing are offset to one lateral side of the longitudinal center line of the tractor, and the tractor is generally referred to as being of the offset type for providing a clear, wide front view from the operator's seat, on the rear of the tractor, particularly for viewing a working implement of mid-mount type, namely an implement attached between the front and rear wheels of the tractor.
In such offset type tractor, the front wheels serve as steering wheels and it is normal to provide junction means for supporting the engine structure solely at the middle of an axle support means for the front wheels, thus substantially in the vertical longitudinal center plane of the tractor. The support junction is therefore laterally offset with respect to the engine, causing the danger of engine distortion, and since the engine weight not only produces a vertical bending moment but also a torsional moment on the connection surface between the engine and the transmission casing, there is also the danger of causing deformation and damage in said connection surface.
In order to eliminate such danger, it is necessary to provide substantially thick walls both for the engine and the transmission casing so as to obtain sufficient rigidity, and also to provide proper means for increasing the connection strength between the engine and the transmission casing; this results in increased weight and size of the drive power unit, thus reducing the desirability of the directly connected drive power unit. It should further be noted that the directly connected engine and transmission casing unit for such conventional offset type tractor can not be of identical design with that of the normal type tractor provided with such power unit extending in the longitudinal center plane, because of the particularly required modification in the former for increasing the strength to sustain the offset weight, as already mentioned above.